This present application relates generally to methods, systems, and/or apparatus for improving the efficiency and/or operation of gas turbine engines, which, as used herein and unless specifically stated otherwise, is meant to include all types of gas or combustion turbine or rotary engines, including aircraft engines, power generating engines and others. More specifically, but not by way of limitation, the present application relates to methods, systems, and/or apparatus pertaining to controlling compressor extraction flows during operation to improve engine performance.
In general, gas turbine engines include a compressor, a combustor, and a turbine. The compressor and turbine generally include rows of blades that are axially stacked in stages. Each stage includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central axis or shaft. In operation, generally, the compressor rotor blades rotate about the shaft, and, acting in concert with the stator blades, compress a flow of air. The supply of compressed air then is used in the combustor to combust a supply of fuel. Then, the resulting flow of hot gases from the combustion, i.e., the working fluid, is expanded through the turbine section of the engine. The flow of working fluid through the turbine induces the rotor blades to rotate. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft.
In this manner, the energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, such that the supply of compressed air needed for combustion is produced, and the coils of a generator, such that electric power is generated. During operation, because of the extreme temperatures of the hot-gas path—which may reach between approximately 2400° to 2600° F.—and high rotational velocities, turbine blades are highly stressed with extreme mechanical and thermal loads. Generally, as one of ordinary skill in the art will appreciate, this requires that gas turbine engines be signed to extract air from the compressor and use the air to cool parts in the hot-gas path during operation. This extraction comes at a price, however, as the usage of compressor air in this manner decreases the efficiency of the turbine engine. Therefore, it should be reduced or minimized whenever possible.
As one of ordinary skill in the art will appreciate, conventional engine design generally employs a one-size-fits-all approach to the extraction of cooling air from the compressor, which means the amount of extraction is fixed. A result of this approach is that often engines extract cooling air from the compressor in excess of the amount needed. Given the performance penalty associated with using excess cooling air and the desire to avoid this penalty to the extent possible during the most common operating conditions, the one-size-fits-all extraction capacity generally is sized smaller than the level that might be needed for certain applications, such as for peak power generation during hot ambient conditions, or larger than that needed for other situations, such as base load operations in colder ambient conditions.
To address this issue, some gas turbine systems use technology that allows for a variable level of extraction from the compressor. However, even where variable extraction is available, convention turbine control methods and systems fail to fully exploit this capability such that attainable increases in output and efficiency are realized. Computer-implemented methods and systems are available that measure and monitor engine operating parameters and, from this data, model the engine system such that other operating parameters may be calculated and used to fine-tune operation. In some instances, as discussed in detail below, this type of technology may be modified (as provided herein) and leveraged such that when paired with variable compressor extraction technology, enhanced engine performance may be achieved. As a result, there is a need for improved apparatus, methods and/or systems relating to the controlling of variable cooling air extraction levels such that greater engine output levels, increased efficiency, and/or other enhanced performance are attainable.